This invention is related to a web transport system, and more particularly to a system which delivers a web by intermittent motion to an exposure station, while providing for continuous motion of the web through a developer station.
In certain media processes it is desirable to move a web of material in predetermined increments past a first station, such as an exposure station, where a latent image may be formed on the media or on the web which supports the media. The web containing the latent image is then processed at a second station, such as a developer, which continuously acts upon the web. In such an automated web delivery system, it is necessary to supply the web to the continuous developer without interruption, while providing for intermittent delivery of the same web to the exposure station, followed by dwell of the web at the station for exposure, accompanied by translation of the material for movement to the developer station.
The invention is particularly useful in handling media or web material which has been made in accordance with the systems and teachings of U.S. Pat. Nos. 4,440,846 and 4,339,209, each assigned to the same assignee as this invention and incorporated herein by reference. In such systems, an imaging system includes a photosensitive layer on a donor web comprising microcapsules which contain a photosensitive composition in the internal phase. The image material is exposed to actinic radiation to form a latent image. Thereafter, the material is subject to a uniform rupturing force in a developer whereupon the microcapsules rupture and imagewise release the internal phase. The rupturing force may be applied by a roll-type pressure developer, which forms a force-applying and driving nip between a pair of pressure rolls. These rolls apply a uniform pressure across the width of the web or the sheet material which contains the latent image.
The imaging systems as described in the above-identified U.S. patents are particularly advantageous since they are totally dry systems and do not rely upon the application of wet developing process solutions to produce or develop the image. An image-forming chromogenic material, such as a substantially colorless color former, is typically associated with the microcapsules.
When the microcapsules rupture, a color former image-wise reacts with the developer material and produces a color image. In the embodiments described in these patents, the microcapsules are typically ruptured by passing the exposed imaging webs or sheets through the nip between pressure or calender rolls. The total media may exist in either single sheet or two sheet versions. In the former, the microcapsules and developer composition are both coated onto a single substrate layer or web. In the latter, the microcapsules are carried on a first substrate layer, referred to as a donor sheet or web. The developer composition is coated on a separate second substrate layer, referred to as a receiver sheet. The donor web is subject to actinic radiation, at an exposure station, and the exposed microcapsule layer is brought into contact with the developer layer of the receiver sheet, and the two sheets are then developed together by the application of pressure thereto, by the roll-type developer, with the finished image being formed on the receiver sheet.
It is desirable that the web containing the media be brought into an exposure station and the movement interrupted during exposure. It is also desirable that the latent image be delivered to the pressure roll developer in a continuous state, that is, without linear interruption, since stopping and starting of the developer can cause variations in image density, image quality, and the like. In addition, the starting and stopping can place heavy loads on the bearings and on the drive components due to the high inertial loads and heavy loading pressures involved. Thus, it is desirable that the developer rolls turn continuously during processing of the media.
As a result, it is necessary to provide a supply of web material for the developer while web movement is interrupted at the exposure station. A simplified transport system is required, which provides the necessary storage of web material for the developer, and at the same time defines and provides the required advancement of the web material to the exposure station, followed by the interruption of movement of the web material for exposure, the transport of such image for development, and the positioning of unexposed media at the exposure station. It is also desirable to avoid rapid acceleration of the supply roll in any delivery system since the shearing forces involved could damage the media surface.